GB807137A - Improvements in electric incandescent lamps - Google Patents

Abstract

807,137. Electric incandescent lamps. GENERAL ELECTRIC CO. July 20, 1956 [Aug. 3, 1955], No. 22524/56. Drawings to Specification Class 39(2) An electric incandescent lamp comprising a bulb of a temperature resisting vitreous material, a filament of substantially pure tungsten, and a gas filling of iodine or a mixture of iodine and inert gas, is characterised by an iodine content of at least about 0.01 micromole per c.c. of bulb volume, and not more than about 1 micromole per c.c., to effect regenerative gettering at a rate to maintain the bulb walls free from blackening without causing substantial absorption of light by the vapours, and the bulb walls are in close vicinity to the filament, the bulb size and shape being so proportioned relative to the filament proportions that, during operation, the bulb has an approximate uniform internal wall temperature within the range of about 250‹C. to 1250 ‹C. The bulbs or envelopes are preferably small and of tubular form, made of quartz or fused silica composition, e.g., containg about 96 per cent. silica. The gas filling to which the iodine is added may comprise argon, krypton or xenon at a substantial pressure for example argon at a presure of 600 m.m. of mercury. The normally cooler parts such as the ends of a tubular envelope may be provided with heat retaining means such as a coating of platinum paint to help maintain the temperature within range specified. Constructional dimensions of comparatively small tubular lamps for respective loadings of 500 watts at 120 volts, and 25 watts at 6 volts, are given in the Specification. Such lamps may be mounted in an outer bulb similar to conventional incandescent lamp bulbs, and the temperature of the inner bulb may then be controlled, in part, by employing a filling of nitrogen in the outer bulb as a cooling medium.